1. Field of the Invention
This invention relates to integrated circuit (IC) fabrication technology, and more particularly, to a method for use in a chamber used in IC fabrication to adjust for parallel alignment between a shower head and a heater platform in the chamber, so that later the deposition process performed in the chamber can result in an evenly deposited layer on the wafer.
2. Description of Related Art
As IC fabrication technology advances to the submicron level of integration, the fabrication processes become more critical. Any minute errors in the fabrication can lead to a complete failure to the fabricated IC product. Should this be the case, the fabricated IC product may have to be discarded. This makes the IC fabrication quite wasteful and costly to carry out.
Deposition is a highly critical process in IC fabrication. There are two major deposition techniques in IC fabrication: physical-vapor deposition (PVD) and chemical-vapor deposition (CVD).
A deposition process, whether PVD or CVD, is customarily performed in a sealed vacuum chamber. The chamber includes a shower head and a heater platform therein. During the deposition process, the wafer is placed on the heater platform while vapor or gases is applied to the wafer from the shower head. To allow precise fabrication, the shower head and the heater platform should be precisely horizontally-oriented; otherwise, the deposited layer is unevenly dimensioned in thickness.
FIG. 1 is a schematic diagram used to depict a conventional method to achieve the foregoing purpose. As shown, the method of the invention is applied to a chamber 10 having a top cover 12 and a bottom cover 14 (in FIG. 1, the top cover 12 is open). A shower head 18 is mounted in the recessed portion 16 on the under side of the top cover 12, while a heater platform 22 is mounted in the recessed portion 20 of the bottom cover 14. A pair of level-adjusting devices 24, 26, each being composed of a threaded bar and a nut screwed onto the threaded bar, are provided beneath the heater platform 22, preferably on opposite sides of the heater platform 22. The technician can manually turn the threaded bars to level the heater platform 22.
By the conventional method, the top cover 12 is flipped open from the bottom cover 14, and then several displacement gauges 28, 30 are placed on the heater platform 22 above the level-adjusting devices 24, 26. The technician then manually turns the threaded bars in the level-adjusting devices 24, 26 while visually checking the level indications from the displacement gauges 28, 30 until all of them are level. After this, the displacement gauges 28, 30 are removed, and then the top cover 12 is closed again. At this stage, however, although the heater platform 52 is level, the gap between the shower head 18 and the heater platform 52 may not be even, i.e., the space at one point may be wider than at another point. A solution to this problem is to actually perform a deposition process on a wafer (not shown) placed on the heater platform 52, and then measure the thickness of the material distributed over the wafer by the deposition process for use as a reference for further adjustment. The deposition and adjustment typically need to be performed several times until the deposited layer is evenly thick over the wafer.
It is apparent that the above-mentioned conventional method is quite laborious to carry out and is also wasteful of wafers. Moreover, since the gap between the shower head 18 and the heater platform 22 is inconsistently fixed in dimension, the fabricated wafers from different chambers are inconsistent in quality.